1. Treatment of NG108-15 neuroblastoma-glioma hybrid cell results in marked increases in the abundance of certain species of RNA. Seventeen cDNA clones corresponding to these species of RNA were obtained and the nucleotide sequences of three clones were determined. DNA clone NG-32 corresponds to mRNA for ATP synthase subunit 6, which is transcribed from the heavy chain of mitochondrial DNA and codes for a protein that is part of the H+ channel of the ATP-synthase complex. Clone NG-10 DNA corresponds to another mitochondrial DNA of unknown function, which is transcribed from the light chain of mitochondrial DNA and may be involved in the initiation of replication of mitochondrial heavy strand DNA. 2. Eleven cDNA clones were obtained that correspond to mRNA for the alpha-subunit of the L-type voltage-sensitive calcium channel of rat brain. Analysis of the DNA sequence and the deduced amino acid sequence reveals strong homology between brain and skeletal muscle calcium channel alpha-subunits. Approximately 75% of rat brain alpha-subunit amino acid residues that were defined are either identical to the amino acid residues of rabbit skeletal calcium channel alpha-subunit or are conservative amino acid replacements. 3. Four novel Drosophila homeobox genes NK-l, -2, -3, and -4 were cloned and partial nucleotide sequences were determined. One NK- 1 cDNA clone was obtained from a cDNA library prepared from poly A+ RNA from 3-12 hr Drosophila embryos, but none was detected in the 0 to 3 hr embryo library. Six NK-3 cDNA clones were obtained from a library prepared from Drosophila poly A+ RNA from 0 - 3 hr embryos and 6 additional clones were obtained from a library prepared from 3 - 12 hr embryo poly A+ RNA. The exon-intron structure of the NK-1 gene was determined. One of the two introns found resides within the homeobox.